The present invention relates to a new and improved construction of apparatus for localization of a line fault in which there is formed from the voltage and current at a measuring or test location at least one signal (traveling wave signal) associated with a traveling wave on the line and its variation as a function of time at the measuring location.
In particular the instant invention is an improvement upon that disclosed in the commonly assigned, copending United States application of Otto Lanz and Michael Vitins, filed Apr. 14, 1976, Ser. No. 676,983, entitled "Method And Apparatus For Locating A Fault On A Line" and the disclosure of which is incorporated herein by reference. While the instant invention can be beneficially used with the therein disclosed circuitry it can be also employed with other equipment for fault location localization operating with traveling waves.
In the just-mentioned copending application there is disclosed an apparatus for locating a fault, i.e. for determining the direction and/or distance of a fault location with respect to a measuring location on a line, with the aid of so-called traveling wave signals. In this context there is to be understood the temporal progression or variation as a function of time at the measuring location of a traveling wave which propagates through the line in the one or the other direction. The apparatus functions with pairs of oppositely moving traveling wave signals, i.e. traveling wave signals which are associated with oppositely moving traveling waves on the line.
These traveling wave signals are formed from measurement signals corresponding to the temporal progression i.e. the course as a function of time of the voltage and current at the measuring location. These signals are hereinafter briefly referred to as the measurement voltage and measurement current respectively. Formation of the traveling wave signals is carried out by additively and subtractively superimposing and measurement voltage and the measurement current, and generally the measurement current or also the measurement voltage is multiplied by a factor.
In particular it is here assumed in the disclosure to follow that the measurement current is directly multiplied by a factor having the significance of an impedance, but with suitable standardization of the magnitudes of the traveling wave signals there can be also utilized multiplication of the measurement voltage by a factor which then has the significance of the reciprocal impedance.
Furthermore, there is always required a pair of measurement voltages and measurement currents which, in consideration of the line inductances and line capacitances, are independent of other voltages and currents respectively. This condition is fulfilled anyway in the case of an aboveground single-line system which is not affected by other lines. In a multi-conductor system there is to be detected for each line a voltage-current signal pair at the measuring or test station, and from which there are to be formed by means of conventional modal resolution appropriate fictitious and mutually decoupled i.e. independent voltage-current signal pairs. From the latter there is then formed by suitable linear combination with the elements of modal matrices, which can be definitely calculated from the given partial inductances and partial capacitances of the conductor system, oppositely moving traveling wave signal pairs for the fault location determination.
In the description to follow for the sake of simplicity reference will be made to a single-conductor system.
The apparatus disclosed in the aforementioned copending application for the fault location determination functions in a faultless manner as long as the measurement voltage in the presence of a short-circuit does not breakdown to too low values, i.e. as far as the measuring location is concerned the fault location positions are not too close. For near faults having correspondingly intense voltage breakdown there are however present difficulties due to the measurement voltage amplitude approaching the disturbance or interfering signal peak following the short-circuit.